Gemstone



FIG. 1 is a front left side perspective view of a gemstone having the design, other corresponding quadrant perspective views being the same;

FIG. 2 is a front plan view thereof;

FIG. 3 is an elevation view taken at the midpoint between the bottom and right side corners, the other midpoint quadrant elevation views being the same; and,

FIG. 4 is a back plan view thereof. 

The ornamental design for a gemstone, as shown and described. 